An extraterrestrial impact 13,000 years ago wiped out mammoths and started a mini-ice age, scientists believe

Margaret Munro CanWest News Service

Monday, May 14, 2007

A comet or some other extraterrestrial object appears to have slammed into northern Canada 12,900 years ago and triggered an abrupt and catastrophic climate change that wiped out the mammoths and many other prehistoric creatures, according to a team of U.S. scientists.

Evidence of the ecological disaster exists in a thin layer of sediment that has been found from Alberta to New Mexico, say the researchers, whose work adds a dramatic and provocative twist to the decades-old debate about the demise of the mammoths, mastodons and sloths that once roamed North America.

The sediment layer contains high concentrations of iridium, fullerenes and other compounds associated with space rocks and impacts, says Luann Becker, a geologist at the University of California, Santa Barbara, who has been analyzing the sediments.

"We have evidence for distribution of impact debris over several thousands of miles over the North American continent," says Ms. Becker, whose group will detail the findings at the American Geophysical Union meeting on May 24.

The sediment layer formed 12,900 years ago and coincides with both the extinction of the animals and the onset of a mini-ice age that lasted more than 1,000 years, say Ms. Becker and her colleagues from several U.S. universities and research labs. They say they are increasingly convinced the impact, extinction and cold snap are all related.

According to their scenario, a comet or large meteoroid generated a shock wave and threw massive amounts of debris, heat and gas into the atmosphere. This set off wildfires that raced across grasslands in southern North America, depriving the mammoths and other grazing animals of food.

The impact and heat also destabilized the ice sheet that blanketed Canada at the time, creating a flood of melt water that poured into the North Atlantic, according to their theory. The pulse of fresh water then shut down the ocean currents carrying heat from the tropics to the Northern Hemisphere, leading to an abrupt cooling. The resulting "mini-ice age" in the Northern Hemisphere, known as the Younger Dryas, lasted more than a thousand years.

Until now one of the leading explanations for the disappearance of the mammoths and other animals is that they were hunted to extinction by the people who arrived in North America from Asia at least 13,000 years ago.

But Ms. Becker and her colleagues doubt there could have been enough people to drive the creatures to extinction with spears. "It would have been a real challenge to slaughter all the animals," she says.

The leading explanation for the mini-ice age has been that melt water slowly built up behind the ice dams as the Earth warmed at the end of the last ice age and then suddenly burst, sending fresh water pouring into the North Atlantic.

Skeptics are not convinced an extraterrestrial impact explains either the disappearance of the animals or the mini-ice age, let alone both events.

Climatologist Andrew Weaver of the University of Victoria says the notion that an extraterrestrial impact caused the Younger Dryas "requires an extraordinarily huge leap of faith." He says there were many climate swings during the last glacial cycle; the mini-ice age was simply the last of them and does not require an extraterrestrial explanation.

Geophysicist Jerry Mitrovica at the University of Toronto is also skeptical. "I'll wait to see the published papers," says Mitrovica, who has studied how the melting ice helped trigger the miniice age.

While the idea of a comet impact may seem far-fetched, Mr. Mitrovica notes that it took almost a decade before scientists accepted geologist Walter Alvarez's evidence that the iridiumrich layer he found pointed to the asteroid impact that killed off the dinosaurs 65 million years ago.

Ms. Becker says the details of their findings will likely be published in the science journals this summer. Meantime, she and her colleagues are expecting a "spirited" debate at next week's AGU meeting.

She says the concentration of the iridium in the sediment layer dating back to 12,900 years is several times higher than normal. It also contains compounds called "fullerenes" with extraterrestrial gases in them, as well as glasslike carbons that require extraordinarily high temperatures to form. "It's a very discrete, well-defined layer," she says.

As for the crater created by the impact, the scientists say it would have formed on the kilometres-thick ice that covered Canada at the time and melted away with the ice.

Does Al Gore know about this? Does he know that there are things other than SUVs and power plant emissions that can cause changes in the earth’s climate? How did our cave man ancestors survive this global cooling?

I'll buy the ice-dam theory combined with a meteor ~ the ice-dam thesis explains where the massive flood waters came from (and we can see the evidence in many locations), and the Canadian residual icecap explains the absence of a crater.

The meteor hits the atmosphere; makes a noise; the dams break; massive quantities of water spill out into the St. Lawrence and Mississippi valleys.

Those waters spread out over the Gulf of Mexico, etc. and interrupt the haline circulation in the North Atlantic.

A sudden refreeze happens. The Sa'ami find they can travel to America along the edge of the winter sea-ice (eating seals the whole way), and arrive there just in time to find all the large game dead, the sabertooth tigers and direwolves expired (from want of game), and the world to themselves as the TOP PREDATOR.

All makes sense. Yup.

About 4,000 years later the same sort of thing happens in Antarctica. Large icedams surround the (much extended) coast, kept cool by the circumpolar cyclone, and melt water backs up behind them.

A meteor hits the atmosphere with enough force to make a loud noise which causes cracks to occur in the icedams which then break.

Vast quantities of water are suddenly released into the ocean causing a tsunami that rushes Northward to flush every coast on Earth of every living thing.

Only those who lived on top the coastal mountains or far inland, or in deep caves, survived to tell the story.

Regarding Antarctica, I think that meltdown was first though, so make that "the other way around". Antarctica's meltdown happens first; kills almost everybody, and then the Lesser Dryas event happens, killing all the big game in America (but not Asia).

Good show Lesser Dryas. You rarely see such detailed selectivity in a Climate Adjustment.

How did all of the megafauna disappear worldwide in a short period? My hypothesis is that ancient man discovered that an atlatl with poison could be launched from a safe 100 yard range at critters large enough for a BIG BBQ. That’s why smaller game, e.g., deer survived and megafauna became extinct. The Aleuts used small harpoons thrown with atlatls from kayaks to kill 40 ton whales. They used aconite from the roots of Monkshood flowers as the poison. Nicotine would work too. A few hundred years of such BBQs and good times would increase the human population manyfold and wipe out animals vulnerable to such hunting techniques.

"But Ms. Becker and her colleagues doubt there could have been enough people to drive the creatures to extinction with spears. It would have been a real challenge to slaughter all the animals," she says.

I must have said this 50 times on FR the last seven years but, does anyone listen to me, noooooo!

"A sudden refreeze happens. The Sa'ami find they can travel to America along the edge of the winter sea-ice (eating seals the whole way), and arrive there just in time to find all the large game dead, the sabertooth tigers and direwolves expired (from want of game), and the world to themselves as the TOP PREDATOR."

I have a very incomplete understanding of the science of these impacts, but the idea that a large impact triggered the end of the last ice age makes sense to me. Triggering the Dryas seems a little out there, but you never know.

12,900 years ago is but a blink of the eye regarding Earth. Yet the world was such a different place back then. One can only imagine how Earth will be 12,900 years from now!

Recorded human civilization has only been around for a few thousand paltry years. Even 200 years ago, life was radically different for humans than it is today. No computers, airplanes, automobiles, telephones, electricity, indoor plumbing, etc.

Forget about global warming and "man-made changes" to the climate. At various intervals, most of North America was covered under thousands of feet of solid ice during the Ice Ages. These times will come yet again no matter how much we cut back on our "emissions" to curb "global warming."

I would like to be given the powers of immortality and go back in time to 25 million years ago. I would like to take with me every book ever published, every music recording ever made and every movie/TV show ever made as well as every bottle of wine and beer ever made just so I will have something civilized to do during those millions of years of non-human civilization. (Of course, I would like a power source to run all these things as well.)

This will allow me to observe the Earth for 25 million years and record everything in detail. Then as human civilization took shape, I would like to be an observer for Ancient Egypt, the Roman Empire, the Middle Ages, the Renaissance and of course, all of U.S. History. I would like to journey with the Pilgrims to New England and be on hand to observe first-hand the entirety of U.S. history.

I would like to drink beer with Benjamin Franklin, go horse riding with George Washington, have a duel with Alexander Hamilton (though not kill him), take in a play with Abraham Lincoln (though stay away from "Our American Cousin") and freak out Albert Einstein by talking about the theory of relativity with him before he even thought of it.

BTW, the reason the Sa'ami could travel along the Southern edge of the Winter sea ice from the Western Refugia to the Grand Banks would have been the disappearance of the Gulf Stream and other currents due to the stoppage of haline circulation by all that tremendous outflow of freshwater into the Mid and North Atlantic.

Without those currents the icebergs breaking out of the sea ice wouldn't have gotten much momentum ~ making travel in a small boat relatively safe even in mid-ocean. I would imagine this would even have a serious impact on hurricanes and that would have extended the sailing time into the warmer months giving the Sa'ami plenty of time to reach America.

I think we can come up with a specific date for when the first Europeans could have arrived in America via an Atlantic route now.

According to their scenario, a comet or large meteoroid generated a shock wave and threw massive amounts of debris, heat and gas into the atmosphere. This set off wildfires that raced across grasslands in southern North America, depriving the mammoths and other grazing animals of food.

Question - what recorded blast started wildfires? Every high temperature blast, that I have seen record of, cooked (sometimes to charcoal) things exposed to them, yet I see no references to fire resulting from them.

There have been a large number of volcanoes that have erupted in recorded history, yet it has only been lava flows that I have heard of starting fires. I believe it was incendiaries, not high explosives that started the firestorms that immolated cities in WWII.

"Without those currents the icebergs breaking out of the sea ice wouldn't have gotten much momentum ~ making travel in a small boat relatively safe even in mid-ocean. I would imagine this would even have a serious impact on hurricanes and that would have extended the sailing time into the warmer months giving the Sa'ami plenty of time to reach America."

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